1. Field of the Invention
This invention concerns a vane adjustment mechanism used in a variable-capacity turbine to control the quantity of exhaust gas. The vane adjustment mechanism has fewer parts and a simpler configuration than its predecessors, which will operate in a stable fashion, and which will be highly durable. This invention also concerns the assembling method for the vane adjustment mechanism.
2. Description of the Related Art
The question of how to make exhaust gases cleaner, i.e., how to reduce the harmful nitrous oxides (NOx) and particulates in the exhaust, has become an environmental concern, particularly with respect to diesel engines. On the other end of the spectrum, the dynamic capability of a diesel engine, i.e., its torque and its output, can be increased by installing a turbocharger. In a turbocharger, a turbine powered by the exhaust gas is used to drive an air compressor which can supply a large quantity of intake air to the engine. Forcing more air into the engine will boost the rate of combustion in the engine and so increase its output.
Since the details of turbochargers are known to the public, we shall not explain them here; however, one means which has been employed to meet the demands in a diesel engine, as well as to increase its dynamic capabilities, is a turbocharger with a vane adjustment mechanism equipped with variable capacity vanes to control the quantity of exhaust gas from the engine.
As can be seen in FIG. 7, the vane adjustment mechanism 51 to control the quantity of exhaust gas lies within turbine housing 61 of turbocharger 60, which is installed on intake pipe E1, which runs into engine E, and exhaust pipe E2. Mechanism 51 is on the outside of turbine blades 63 on one end of shaft 62. In FIG. 7, 64 is the compressor impeller provided on the other end of turbine shaft 62.
A prior art design for a vane adjustment mechanism 51 to control the quantity of exhaust gas is shown in FIGS. 8 and 9. 52 is a base unit formed by a short pipe member on the end of which is base flange 52a. The turbine blades 63 fit inside the interior of base unit 52 and are coaxial with it.
A second flange, 52b, is formed on the end of base unit 52 opposite of that where flange 52a is formed. A number of vane shaft holes 52c, which are equal in number to the nozzle vane units 53 that go from flange 52a to flange 52b. A cover 52d protects nozzle vane units 53, which will be discussed shortly, on flange 52a. 
Each nozzle vane unit 53 is a variable capacity vane, and it has a vane shaft 53a slipped into vane shaft hole 52c, which fits to the vane shaft 53a. The nozzle vane unit 53 protrudes from flange 52a at a right angle with respect to the surface of that flange. The angle of inclination of the surface of the nozzle vane unit 53 can be adjusted between a radius angle and an arc angle with respect to the center of base unit 52. One end of vane shaft 53a has nozzle vane unit 53, and the opposite end of the vane shaft 53a is fixed by riveting to the drilled hole 54a of lever 54, to be discussed shortly.
54 is a lever on top of flange 52b. The number of these levers 54, is equal in number to the nozzle vane units 53. A through hole 54a is provided on one end of lever 54 through which vane shaft 53a of nozzle vane unit 53, runs through to base unit 52. On the other end of lever 54, on the surface opposite that of which nozzle vane unit 53 is located, is a protrusion 54b, which engages with one of holes 55a of link plate 55, which will be discussed shortly.
The end of vane shaft 53a of nozzle vane unit 53, the insert shaft in hole 54a of lever 54, is riveted so that the nozzle vane unit 53 and the lever 54 form a single piece. Thus, both of the nozzle vane unit 53 and lever 54 are connected through base unit 52. Since the end of vane shaft 53a is riveted, the movement of lever 54 will change the angular orientation of the surface of nozzle vane unit 53.
55 is a link plate. The rounded center portion of link plate 55 engages with the outer surface of base unit 52. There is an eccentric hole 55a over the arc of the rounded portion, in which protrusion 54b of lever 54 engages. Link plate 55 also has a link portion 55b on a portion of the circumference of the plate, to engage with actuator unit.
A vane adjustment mechanism 51 to control the quantity of exhaust gas configured as described above is driven with an actuator (not pictured) connected to link portion 55b of link plate 55. When link plate 55 rotates over a given angle of rotation, the protrusion 54b of lever 54 rotates, and the other end of lever 54 which is fixed to the vane shaft 53a also rotates. In this way vane shaft 53a is made to rotate as a shaft, and the angle of nozzle vane unit 53 changes. A vane adjustment mechanism 51 which is driven in this way can adjust the quantity of exhaust gas to turbocharger 60 so as to optimize the function of the engine.
The prior art vane adjustment mechanism 51 to control the quantity of exhaust gas, which is shown in FIGS. 8 and 9, requires that the vane shaft hole 52c, provided in base unit 52 for vane shaft 53a of nozzle vane unit 53, be drilled to precise dimensions. Forming such a hole 52c during the manufacture of mechanism 51 requires careful labor. Also, because vane shaft 53a must fit closely in vane shaft hole 52c, particulates in the exhaust gas which adheres to its surface will fuse to the inserted shaft and the surface of vane shaft hole 52c, adversely affecting its durability.
The prior art vane adjustment mechanism 51 has a lever 54 and a vane shaft 53a which are riveted together. This requires a number of components, such as vane shaft 53a (nozzle vane unit 53) and lever 54, thus increasing both the parts count and the number of assembly processes. Just as was discussed earlier, these components also require a high degree of precision machining. Determining the correct position (i.e., the proper angle) at which to fix nozzle vane units 53 to levers 54 also required a high degree of precision.
In prior art vane adjustment mechanisms 51, the same problem as described above was experienced between hole 55a in link plate 55 and protrusion 54b of lever 54.
The high degree of machining precision which is required in prior art vane adjustment mechanism 51, to control the quantity of exhaust gas required in order to withstand being used under severe conditions in a turbocharger, increased the labor and the cost required to produce it. In addition, it required a large number of components, which complicated its configuration and increased the production time, reducing the efficiency of production and increasing its cost.
This invention was developed to solve the problems described above. The object of this invention is to provide a vane adjustment mechanism to control the quantity of exhaust gas, which will have fewer components and a simpler design, which will operate in a stable fashion, and which will be extremely durable.
In order to achieve these objectives, the vane adjustment mechanism, according to this invention, has the following essential features. With respect to the base unit and the link plate in which holes were formed by drilling, according to the prior arts vane adjustment mechanism, this invention uses a U-shaped indentation so as to eliminate the drilling process for forming a through hole. With respect to the components to adjust the vanes and the levers in a prior art mechanism to control the quantity of exhaust gas, which were composed of numerous parts, this invention uses a single part for the purpose of reducing the parts count. With respect to the insert shaft in the vane lever unit, which was linear in the prior art mechanism to control the quantity of exhaust gas, this invention narrows the diameter of the insert partway along its length in order to reduce the precision machining process for making the shaft. By selecting some or all of these improvements, the manufacturer can reduce the number of parts required, simplify the configuration of the mechanism, improve its operational stability and durability, and improve the assembling method for the vane adjustment mechanism.
The vane adjustment mechanism to control the quantity of exhaust gas which is disclosed in this application has a base unit having the shape of a short pipe, which has a first flange on an outer surface and a second flange on the inner side in the direction of exhaust gas; a plurality of vanes positioned along the circumference of the base unit, which adjust the quantity of exhaust gas; a link plate provided on the second flange of the base unit, whose inner circular edge engages with the outer edge of the base unit in such a way that the link plate is free to rotate; and a plurality of vane lever units connecting the plurality of vanes and the link plate, which run through vane shaft holes in the base unit.
The mechanism is distinguished be the following configuration. The base unit comprises an inner base unit having the first and second flanges, and an outer base unit into which the inner base unit 2A is forced, and a plurality of U-shaped indentations spaced at regular angular intervals on the inside surface of the inner or outer base unit from the first flange to the second flange, so that the U-shaped indentations form the vane shaft holes to accommodate the vane lever units when the inner base unit is forced into the outer base unit to block the U-shaped indentations in such a way that the vane lever units are free to rotate. In the assembling method according to this invention, the same features are distinguished from the prior art.
When the inner base is forced into the inner base in this fashion, a portion of each indentation will be blocked. As a result, the indentations will function as vane shaft holes. In other words, if indentations are provided on either the inside of the outer base unit or the outside of the inner base unit, no punching process will be needed. Furthermore, there will be less area which must be finished with a reamer, so the work required to manufacture the mechanism is simpler.
The vane and the vane lever unit are formed as an integral piece. As an actual configuration, it has vane units placed on top of the first flange, each of which consists of a vane whose surface is orthogonal to that of the first flange; and levers, each of which consists of a vane shaft extending from the vane unit toward the second flange and engaging in one of the indentations; a connector linked to this vane shaft which lies parallel to the surface of the second flange; and a protrusion which is linked to this connector and runs perpendicular to the surface of the second flange. The vane unit and lever are formed as an integral piece.
By forming the vane unit and lever as a single piece, we can reduce the parts count and by the same token reduce the number of assembly processes. In addition, we eliminate the need to determine the correct angle between the lever and the surface of the vane unit, which reduces the labor required.
The link plate has U-shaped cutting or concaved indentations, in which protrusions of the vane lever unit engage, all along the circumferential edge of the link plate. When compared with the process of providing holes in the link plate, this process provides superior strength with respect to thermal deformation and is easier to perform.
The mid-portion of a vane shaft of the vane lever unit has a narrow portion which has a smaller diameter than the ends of the vane shaft, which reduces the contacting surface area with the U-shaped indentation so preventing the vane shaft from seizing in the U-shaped indentation. Making the central portion of the vane shaft narrower will keep the vane shaft from coming in less contact with the surface of the indentation. This will eliminate the need for precision finishing and so shorten the production time by that amount. It will also prevent the parts from seizing.